Cyclonic vacuum cleaners work using cyclonic action to separate out dust and dirt from the dirty air sucked into the cleaner. They generally comprise at least one cyclonic chamber in which the air spins at high speed under the prevailing vacuum pressure, and a respective dirt collection chamber which is arranged to collect the dirt flung out from this fast-spinning airflow. The cyclone chamber and dirt collection chamber are together referred to as a cyclonic stage of separation.
The separation efficiency of a cyclonic stage varies with particle size. Consequently, in order to deal with the range in particles sizes typically found in household dust, a tuned series of cyclonic stages is typically provided. In this sort of multi-stage arrangement, the first stage tends to remove the relatively large particles and then each successive stage is optimized to remove successively smaller particles. The various stages may be packaged together as a single, cyclonic separator, which may be removable from the vacuum cleaner to allow easy emptying of the dirt collection chambers. FIG. 1 shows a typical example of this sort of general arrangement. Here, the vacuum cleaner 1 is an upright vacuum cleaner and a removable multi-stage cyclonic separator 3 is mounted in an upright position on a rolling support assembly 5 forming part of the cleaner 1.
FIG. 2 is a section through the cyclonic separator 3. Here the first cyclonic stage—or ‘primary’—comprises a relatively large, cylindrical bin 7 which acts both as a cyclone chamber and as a dirt-collection chamber. The second cyclonic stage comprises a plurality of smaller, tapered cyclone chambers 9 arranged in parallel (to reduce pressure losses across the secondary stage) which each feed into a second dirt collection chamber 11—the so-called Fine Dust Collector (FDC).
The dirty air enters the cyclonic separator 3 through a tangential inlet 13 on the bin 7 (shown in FIG. 1), which helps impart the necessary spin to the airflow inside the bin 7. The air exits then exits the primary through a cylindrical mesh outlet—or ‘shroud’—15 and from here is ducted to the secondary cyclone stage. The air exits the secondary cyclone chambers 9 through the top and is collected in a manifold 17, from where it ducted down through the bottom of the cyclonic separator 3—via a sock filter 19 (for separating very fine particles remaining in the airflow)—to the vac-motor.